This application claims priority under 35 U.S.C. xc2xa7xc2xa7 119 and/or 365 to 311458/1999 filed in Japan on Nov. 1, 1999; the entire content of which is hereby incorporated by reference.
1. Technical Field
The present invention relates to forming molds that are suited to the manufacture of molded glass articles such as high-precision lenses and do not require cutting or polishing following press molding. The present invention also relates to methods of molding glass articles employing these forming molds. The present invention further relates to methods of assembling formed glass article manufacturing devices suited to the manufacture of formed glass articles such as high-precision lenses.
2. Background Art
A great number of techniques for producing molded glass articles such as high-precision lenses by forming in mold presses have been developed in recent years. These molding techniques can be divided into roughly two categories. In the first method, the glass material to be molded is placed in the forming mold at room temperature outside the molding device. Next, the forming mold into which the glass material to be molded has been placed is placed in the device, a number of sections within the device are moved to conduct heated pressing and cooling, the forming mold is removed from the device, and the molded glass article is removed from the forming mold outside the device.
By contrast, in the second method, a forming mold is employed in which an upper mold and a lower mold are mounted in advance on vertical press shafts within the device. In this method, the glass material to be molded is supplied at room temperature onto the forming surface of the lower mold, and in that state, the forming mold is heated to heat the glass material to be molded. The glass material is pressed, cooled, and removed from the device upon reaching room temperature. However, in the preferred method, the glass material to be molded is heated separately from the forming mold, transferred to the forming mold, pressed (sometimes heated and pressed), and released from the mold once it has been cooled to below the transition point of the glass. The molded glass article is then immediately removed from the mold. Since this method does not require that the forming mold be brought down to room temperature, an extremely short molding cycle and efficient production are possible.
A number of conditions must be satisfied to produce a formed glass article such as a high-precision lens by heating the forming mold to a temperature corresponding to a glass viscosity of 108-1012 poise, heating the glass material being molded to a temperature equal to or greater than that of the forming mold, press forming the glass material being molded with the forming mold, cooling the glass material being molded to below the transition temperature of the glass, releasing the mold, and removing the molded glass article from the forming mold.
The forming surface of the forming mold must be machined to a high surface precision and a fine surface roughness, and must not fuse with the glass as a result of press forming. To perform as a lens, specifications such as thickness, outer diameter, surface precision, eccentricity precision (axial shift, tilt), and outer appearance must be met. Although the formed glass article is released immediately from the mold once cooled to below the transition point of the glass, it is extremely important to achieving stable, continuous production that the upper mold not adhere to the formed glass article during that process and that the formed glass article come out smoothly. During mold release, cooling to below the glass transition point is required to achieve surface precision. Additionally, shrinkage tends to occur when the mold is released at a temperature exceeding the glass transition point. Such problems do not occur at below the glass transition point so long as the glass consolidates.
Further, rapid heating and cooling of the forming mold are desirable from the perspective of improving production efficiency by shortening the molding cycle time to the extent possible.
The present inventors have developed and proposed a forming mold (Japanese Patent Application Publication No. Hei 11-49523) that can be employed in methods satisfying the above-stated requirements. The structure of this forming mold is shown in FIG. 9, and a schematic of the forming method employing this forming mold is given in FIG. 10. However, it has become clear that the following problems tend to occur due to the mold structure in the molding method employing this forming mold.
The molding device for formed glass articles shown in FIG. 9 is equipped with a forming mold 110; a drive mechanism comprised of a cylinder and the like for vertically displacing forming mold upper member 114 in a manner described further below; a heater for heating prescribed members comprising forming mold 110, such as upper mold 120 and lower mold 130; and a high-frequency coil.
Forming mold 110 is roughly cylindrical in shape and comprises a forming mold upper member 112 secured at prescribed positions and a forming mold lower member 114 capable of being moved vertically by a cylinder (not shown). Forming mold upper member 112 is provided with a roughly cylindrical first upper matrix 116, a hollow cylindrical second upper matrix 118 positioned beneath upper matrix 116 and secured to upper matrix 116, and an upper mold 120 inserted into second upper matrix 118 and disposed with a matching center shaft. An upper mold descent stop ring 122 [sic: 127] concentric with, and positioned radially between, second upper matrix 118 and upper mold 120; a sleeve 124, positioned concentrically with upper matrix 118 and upper mold 120 and positioned further to the forming surface side of upper mold 120 than upper mold descent stop ring 122; and a spring 125 pushing against sleeve 124 between upper mold descent stop ring 122 and sleeve 124 are also provided.
Additionally, forming mold lower member 114 is provided with a [first] lower matrix 126, secured on its lower surface to a cylinder (not shown); a hollow cylindrical second lower matrix 128 secured to [first] lower matrix 126, and a lower mold 130, positioned concentrically with [second] lower matrix 128 and configured so as to permit the placing of a glass material onto the forming surface, or upper surface, thereof. [Second] lower matrix 128 is positioned by means of a protrusion 148.
Prior to insertion of lower mold 130 into sleeve 124 (as shown in FIG. 10(b)), the center shaft of the upper mold and the center shaft of the lower mold are not necessarily perfectly aligned. Even once the lower mold has been inserted into the sleeve (as shown in FIG. 10(c)), the sleeve dangles loosely in a vertical direction from the spring. Further, the clearance between sleeve 124 and upper mold 120 on the one hand, and upper matrix 180, on the other, may result in radial shifting. A protrusion for contacting and scraping away the formed article that has adhered to the forming surface of the upper mold is provided on the inner surface of sleeve 124. The clearance between sleeve 124 and the inside of upper mold 120 is adjusted so that when sleeve 124 slides vertically, the protrusion on its inner surface contacts the outermost rim portion of the molded article. Thus, while the clearance in a common forming mold is about 2-10 xcexcm between the drum and the forming mold, in the mold shown in FIG. 10, for the above-stated reasons, the spacing between sleeve 124 and the inside of upper mold 120 ranges from about 0.1 to 5 mm.
Thus, sleeve 124 is kept in a dangling state by the spring and has considerable clearance with the upper mold. There is also a prescribed clearance between lower mold 130 and sleeve 124. Thus, in this state, sleeve 124 sometimes tilts within the above-stated prescribed clearance. When sleeve 124 tilts, a tilt develops between lower mold 130 and upper mold 120. Conducting press molding (as shown in FIGS. 10(d) and (e) by force in this state results in shifting of the optical axis of the lens obtained, precluding eccentricity precision. When the lens obtained is the microlens in a laser optical system, failure results due to frame aberration. When pressing is conducted with the mold in a tilted state, the sleeve bites into the upper mold, no longer moves freely in a vertical direction, fails to be pushed down by the spring during mold release, and as a result, sometimes prevents the molded glass article adhered to the upper mold from being released from the mold.
As a result, it has not been possible to manufacture with high production efficiency molded glass products having high surface precision.
Accordingly, the object of the present invention is to provide a molding device for manufacturing molded glass articles in which the above-stated problems have been solved. That is, the present invention has for its object to provide a molded glass article manufacturing device having a means of forcing release from the mold by contacting the outer rim area of a molded glass article that has adhered to the forming surface of the upper mold or lower mold, in which the shafts of the upper mold and lower mold can be readily and reliably aligned.
A further object of the present invention is to provide methods of molding glass articles in which the above-described forming molds are employed to manufacture with high production efficiency molded glass articles having high surface precision and eccentricity precision.
A still further object of the present invention is to provide a reliable method of advance axis alignment so as to permit molding even when the displacement axes of the upper mold and/or lower mold within a drum or the like are not regulated.
The above-stated objects are achieved by the above-described molded glass article manufacturing device, equipped with an upper mold and a lower mold capable of separating from, and approaching, each other and having opposing forming surfaces, wherein said upper mold and said lower mold separate from each other in the course of supplying a glass material to the forming surface of said lower mold and in the course of removing the molded glass article from the forming surface of said lower mold;
characterized by comprising:
a drum capable of regulating said upper mold and said lower mold so that the displacement axes thereof align;
a forced mold separating means separating said molded glass article adhered to a forming surface from the mold by contact with at least the rim portion of said molded glass object; and
a displacement means for displacing said forced mold separating means relative to said upper mold or said lower mold so that, in the course of separation of said upper mold and said lower mold, said forced mold separating means contacts at least the rim portion of said molded glass article and separates said molded glass article from the forming surface.
The present invention further relates to a manufacturing method for molded glass articles comprising a step of pressing a heated glass material with an upper mold and a lower mold, a step of cooling said molded glass article produced by pressing, and a step of separating said cooled molded glass article from the mold;
characterized in that:
the device of the present invention is employed;
said glass material is pressed so that the outer diameter of said molded glass article becomes larger than the outer diameter of the forming surface of the upper mold in said pressing step; and
the rim portion of said molded glass article and a portion of the forced mold separating means come into contact during the step of separation from the mold and said upper mold and said forced mold separating means are displaced relative to each other so that said molded glass article adhered to said upper mold forming surface is separated from the upper mold forming surface to separate said molded glass article adhered to said upper mold forming surface from the mold.
The present invention further relates to a manufacturing method for molded glass articles comprising a step of pressing a heated glass material with an upper mold and a lower mold, a step of cooling said molded glass article produced by pressing, and a step of separating said cooled molded glass article from the mold;
characterized in that:
the device of the present invention is employed;
said glass material is pressed so that the outer diameter of said molded glass article becomes larger than the outer diameter of the forming surface of the lower mold in said pressing step; and
the rim portion of said molded glass article and a portion of the forced mold separating means come into contact during the step of separation from the mold and said lower mold and said forced mold separating means are displaced relative to each other so that said molded glass article adhered to said lower mold forming surface is separated from the lower mold forming surface to separate said molded glass article adhered to said lower mold forming surface from the mold.
The present invention further relates to a method of assembling a molded glass article manufacturing device equipped with an upper mold and a lower mold capable of separating from, and approaching, each other, said upper mold being secured to an upper main shaft, said lower mold being secured to a lower main shaft, and said upper mold and said lower mold having opposing forming surfaces;
characterized in that said upper mold is directly or indirectly secured to said upper main shaft and said lower mold is likewise secured to said lower main shaft so as to be held in a centering holder in such a manner that the displacement axes of said upper mold and said lower mold are aligned.